In the course of operating a fixed bed gas producer, it is necessary from time to time to check the condition of the fire bed. This is accomplished by inserting a steel rod through a hole in the top of the producer and pushing the rod down through the fuel bed to the top of the grate level, in which position it may be left for several minutes.
When a hole cover is opened to admit the rod, a passage is provided for the hot producer gas to escape through the hole to atmosphere, since this gas is above atmospheric pressure. The temperature of the gas within the producer is near its ignition point, and when the escaping gas meets the atmosphere, it either ignites, producing a long jet of flame, or, if it does not ignite, provides a noxious stream of tar-laden gas. This condition is somewhat reduced when the poke rod is inserted, but the gas continues to escape through the clearance between the rod and the poke hole. Not only does such an operation result in loss of producer gas during the poking operation, but it creates a hazardous situation for the operator.